Nut Drop Research Articles

Nutrient responsiveness and correlation analysis of cashew (Anacardium occidentale L.) cv. Balabhadra for vegetative, reproductive traits and nut yield under coastal Odisha condition

Aim: The aim of the present study was to investigate the effect of nutrient management approaches on vegetative, reproductive growth and yield of cashew, Anacardium occidentale L. cv. Balabhadra. Methodology: Trial was conducted during 2021-22 to 2022-23 to study the foliar application of different macro, secondary and micro- nutrients of cashew plant. The experiment was designed in RBD with six treatments and four replications. Foliar spraying was done at three stages viz., pre-flowering, flowering and nut set stages. Results: Treatment schedules i.e., 100% RDF+10 kg FYM/plant /year+ foliar spray of major nutrients (3% urea+0.5% MAP+1% K2SO4)+ foliar spray of secondary and micro-nutrients (0.5 % ZnSO4 + 0.1 % Solubor + 0.5 % MgSO4) witnessed better performance of cashew for most of the vegetative and reproductive traits under study. Multivariate analysis showed formation of five principal components, where PC1 contributed maximum (97.80 %) towards total variance. Pearson correlation coefficient analysis revealed positive association of yield relevant traits (P < 0.001) and negative correlation for number of flowering laterals and nut drop (%). Interpretation: Foliar spraying of macro, secondary and micronutrients in combination significantly influenced the vegetative and reproductive traits which may influence the nut yield of cashew. Key words: Cashew, Foliar spray, Nutrients

Nutritional constraints for nut drop of arecanut in Western Ghats soils of Uttara Kannada of Karnataka in India

In recent years, nut drop in arecanut crop is becoming a common problem in Western Ghats soils of Uttar Kannada district. To find out the reasons for nut drop in arecanut, a research was conducted during 2010-11 and 2011-12 in the area involving survey of nut drop affected fields, collection of soil samples from the affected fields and their analysis. The soils were analysed for pH, EC, organic carbon, available NPK, DTPA-Zn and available boron. The soils of the area match with the laterite characters. The initial data (before onset of monsoon) indicated that the soils were acidic in lower depths while neutral in surface soils, low in EC, low in available P, DTPA-Zn and available boron. The available K was low to medium. However, the soils were found medium to high in organic carbon and available N. The soil samples were also collected after receipt of rainfall and analyzed. The results indicated that the soil pH was slightly lowered but EC and available K were lowered more as compared to intial values. Similarly the organic carbon and available N were increased but DTPA-Zn and available B were remained low and not affected much as compared to initial status. Depth-wise soil analysis indicated that surface soil were having more acidic pH, low salts, higher organic C, higher available NPK than sub-soils. Further, these were lowered after receipt of rain, particularly EC and potash. The available Zn and B remained deficient. The available K, DTPA-Zn and available B were found to be deficient in these soils and need to be corrected immediately after heavy rains. The nutrients and other soil properties status if not improved may become constraints for nut drop in arecanut. To improve the soil pH, it is necessary to apply lime / dolomite, to improve EC level and available potash status of soil there is a need to apply extra dose of potash to soil than the recommended dose. To increase available P in acidic soils, there is a need to apply rock phosphate. Since the available N is medium to high, the recommended N may be continued. The recommended dose of Zn and B have to be applied before onset of monsoon and if nut drop prevails these have to be applied immediately after receipt of rains.

Acaricidal effects and residues of profenofos and abamectin on the nut-infesting eriophyid mite, Aceria guerreronis Keifer (Acari: Prostigmata) on coconut

In recent years the coconut in south India has been under severe threat from invasion by the eriophyid mite Aceria guerreronis Keifer (Acari: Prostigmata). Since 1998 it has attained a major pest status, particularly in three peninsular states of India, namely, Kerala, Karnataka and Tamil Nadu, and has spread northwards. Severe damage can lead to premature nut drop or extreme reduction in the size of nuts. We evaluated abamectin 1.8 EC (2.5, 5.0 and 7.5 ml), profenofos 50 EC (10, 15 and 20 ml) and monocrotophos 36 SL (15 ml) and applied to roots as aqueous solutions for their efficacy in controlling the mite. Root feeding with abamectin 7.5 ml + 7.5 ml water and abamectin 5 ml + 5 ml water resulted in moderate reductions of 58.84% and 51.44% of the mite population, respectively, and also produced bunches with least damage. The other treatments caused less than 50% reduction in the mite population. No detectable residues were noted for abamectin, whereas in the profenofos treatments residues were detected from 3 to 30 days in the coconut kernel and water in the 15 ml + 15 ml water and 20 ml + 20 ml water treatments after the second round of root feeding. The kernel samples had 0.014 and 0.021 μg/g residues in the 15 and 20 ml treatments, respectively, whereas the residues were below detectable levels in water samples from day 45 after treatment. Hence, a waiting period of 45 days after root feeding is recommended before harvesting of tender coconuts and matured nuts.

Abscission of Control Pollinated Coconut Fruits: Preliminary Investigations into the Possible Role of Ethylene

Recent advances in the spread of the Cape St Paul Wilt disease (CSPWD) necessitate a more rapid development of tolerant coconut types. Control pollination is the main method for producing legitimate coconut seeds for such breeding purposes. However, the process of bagging causes severe nut drop or abscission. Many scientists have implicated hormones as the primary regulators of organ abscission; with ethylene being particularly implicated. Unlike other plant hormones, which are mainly produced in other parts and transported to influence target organs, the production of ethylene could be initiated within the same organ, such as the fruit. This study was therefore undertaken to investigate the possible involvement of ethylene in abscission after control pollination. Pollen from Vanuatu Tall (VTT) variety was used to cross emasculated Malayan Yellow Dwarf (MYD) inflorescence after isolation with bags. Trials were laid out in Completely Randomised and Split Plot designs, with specified replications. Two ethylene inhibitors, namely aminoethoxyvinylglycine (AVG) and silver thiosulphate (STS) were used. Five concentrations of AVG ranging from 2mg/l to 30mg/l were applied to inflorescences during and after bagging. AVG concentrations higher than 2 mg/l resulted in significant reduction in abscission. Fruit yields up to five times that of ordinarily bagged treatments without AVG were recorded. Four concentrations of STS ranging between 0.5mM – 10mM applied in similar manner, however, did not result in any significant reduction in abscission. The results from AVG application strongly suggest the involvement of ethylene in the abscission of control pollinated coconut fruits.

STUDY OF XANTHOMONAS ARBORICOLA PV. JUGLANDIS POPULATION DYNAMICS IN FRENCH WALNUT ORCHARDS OVER THREE YEARS

Walnut blight, caused by Xanthomonas arboricola pv. juglandis is a major disease of Walnut in France, mainly responsible for necrosis on fruits and early nut drop before harvest. The population dynamics were studied over three years in orchards in the South-West of France, with comparison among orchards with different infestation levels. Samples of buds, leaves, flowers, pollen and fruits were collected from the beginning of April till the end of August, and the epiphytic population size of X. a. pv. juglandis was measured by plating dilutions of water extract on Tween Modified Medium. Population size broadly varies during the year from 10 3 to 10 7 cfu/g, increasing from budbreak, and remains stable after flowering. The level is a little lower in less infected orchards, suggesting that the expression of disease is more affected by pedo-climatic conditions than bacterial population level.

Nitrogen use for high productivity and sustainability in cashew

Interest in cashew production in Australia has been stimulated by domestic and export market opportunities and suitability of large areas of tropical Australia. Economic models indicate that cashew production is profitable at 2.8 t ha −1 nut-in-shell (NIS). Balanced plant nutrition is essential to achieve economic yields in Australia, with nitrogen (N) of particular importance because of its capacity to modify growth, affect nut yield and cause environmental degradation through soil acidification and off-site contamination. The study on a commercial cashew plantation at Dimbulah, Australia, investigated the effect of N rate and timing on cashew growth, nut production, N leaching and soil chemical properties over five growth cycles (1995–1999). Nitrogen was applied during the main periods of vegetative (December–April) and reproductive (June–October) growth. Commercial NIS yields (up to 4.4 t ha −1 from individual trees) that exceeded the economic threshold of 2.8 t ha −1 were achieved. The yield response was mainly determined by canopy size as mean nut weight, panicle density and nuts per panicle were largely unaffected by N treatments. Nitrogen application confined to the main period of vegetative growth (December–April) produced a seasonal growth pattern that corresponded most consistently with highest NIS yield. This N timing also reduced late season flowering and undesirable post-November nut drop. Higher yields were not produced at N rates greater than 17 g m −2 of canopy surface area (equating to 210 kg N ha −1 for mature size trees). High yields were attained when N concentrations in Mveg leaves in May–June were about 2%, but this assessment occurs at a time when it is not feasible to correct N deficiency. The Mflor leaf of the preceding November, used in conjunction with the Mveg leaf, was proposed as a diagnostic tool to guide N rate decisions. Leaching of nitrate-N and acidification of the soil profile was recorded to 0.9 m. This is an environmental and sustainability hazard, and demonstrates that improved methods of N management are required.

Macadamia responses to mild water stress at different phenological stages

Mild water stress was imposed on bearing macadamia trees in through-draining lysimeters at various phenological stages. Water was withheld until a xylem water potential (Ψx) of –1.5 to 2.0 MPa was reached, this being maintained by partial water replenishment at 2-day intervals. Flowering, nut set, nut development, yield, and quality responses were assessed to identify critical, stress-sensitive stages. Stress during nut maturation was particularly detrimental to both yield and quality, although stress during floral development and the premature nut drop also had adverse effects. Low yields were due to reduced nut number and smaller nuts. Lower photosynthesis (c. 2 μmol CO2/m2.s) at –1.5 MPa would account for reduced yield and poorer quality during nut maturation when energy demands of active oil accumulation are high. Stress at floral initiation was generally not detrimental.Overall, stress restricted growth. The rate of girth growth was significantly lower when stress was applied during the dormant floral initiation stage. When stress coincided with normal periods of vegetative growth, flushing was delayed until after re-watering when greater foliage production was stimulated. Judiciously imposing mild stress may be used to manipulate macadamia phenology, although it may not necessarily conserve water. Further refinement would be needed to develop stress manipulation as a practical and reliable management tool to achieve higher yields. Water should be applied to alleviate stress during critical stages of nut development and maturation. Mild stress after the current crop is mature, however, is unlikely to be detrimental to macadamia yield or quality. It may, in fact, be beneficial through manipulation of flushing patterns that influence yield.

Insect Damage Estimates for ‘Stuart’ Pecan Nutlets from Nut Set to Shell Hardening in Insecticide-Treated and Untreated Trees

Pecan nut loss due to pecan nut casebearer, Acrobasis nuxvorella Neunzig, damage was significantly lower in the chlorpyrifos-treated, ‘Stuart’, pecan trees (0%) than in untreated trees (16%). Percentage loss due to nut drop from all causes between nut set and shell-hardening was significantly lower in the treated (27%) than in the untreated trees (42%). Treated trees had significantly higher average yield (38 kg/tree) than the untreated (29 kg/tree). Nut size was significantly smaller in untreated (156 nuts/kg) than in treated trees (145 nuts/kg). Monitoring the fate of ‘Stuart’ pecan nutlets from nut set to harvest indicated that the number of nuts/cluster at nut set was often positively correlated with kernel weight at harvest, whereas, nut cluster size later in the season was positively correlated with kernel weight at two orchards and negatively correlated with kernel weight in the control treatment at a third orchard. A commercial orchard where pecan nut casebearer, hickory shuckworm, Cydia caryana (Fitch) and nut curculio, Conatrachelus hicoriae Schoof, were controlled with insecticide sprays in the spring had similar total nut drop over the entire season as an orchard where these insects were not controlled. The majority of the pecans that dropped from the trees did not have discernible signs of plant disease, insect feeding damage or insect oviposition.

188 Effect of Streptomycin Walnut Blight Sprays on Nut Drop

Walnut Blight caused by the bacteria Xanthomonas campestris pathovar juglandis is a very destructive disease for California walnut production. Streptomycin is an effective disease control material; however, Streptomycin sprays can result in significant nut drop 3 to 5 weeks after spray application. We investigated the basis for walnut drop following applications of Streptomycin (Agrimycin) for walnut blight control. Flowers and developing nuts were collected from four treatments, plus an unsprayed control. 200 ppm Streptomycim was applied at 1) budbreak; 2) pre, full, and post-bloom; 3) postbloom; 4) budbreak and postbloom; 5) untreated control. Samples were collected regularly beginning at the first budbreak spray and extending through the period of nut drop. Samples were fixed and prepared for histological examination. In treatments with a high incidence of nut drop, the embryo failed to develop. Examination of the stigma and style in flowers from these treatments showed inhibited pollen tube growth. Results indicate that Streptomycin inhibits pollen tube growth, which precludes fertilization. This pattern of development and timing of nut drop following Streptomycin application at full bloom is similar in all ways to unpollinated walnut flowers. Nut growth and development appear normal for 3 to 5 weeks; then nuts abort. If Streptomycin became available for walnut blight control, sprays timed to coincide with pistillate bloom and pistillate flower receptivity should be avoided.

Nitrogen and environmental factors influencing macadamia quality

Applications of nitrogen fertiliser in macadamia orchards remain high, despite indications that optimum yields and quality are obtained at a lower rate. This 6-year study examined the effect on quality of 230, 690 and 1150 g nitrogen/tree . year, applied in April (floral initiation), in April and June (inflorescence development), in April, June and November (rapid nut growth and premature nut drop), in April, June, November and January (nut maturation/oil accumulation) or monthly. Higher rates of nitrogen increased kernel recovery by 1% in 5 years out of 6. In 1 year only, 4 or more split applications of the medium and high rates of nitrogen increased kernel recovery by up to 1.6%. These increases were insufficient to compensate for depressed yields (17% lower) at high nitrogen. In good years, when yields were above average, kernel recovery tended to be high and in years with poor yields, kernel recovery tended to be low except when nuts were small. Moderate summer—early autumn rainfall of about 100 mm/month was associated with high kernel recovery whereas very heavy rainfall (>200 mm/month) during this period was detrimental. The percentage of first grade kernels was influenced most by season but was negatively correlated with the rate of nitrogen. Impurities, including immature, deformed, mouldy and insect-damaged kernels, were lowest at low rates of nitrogen and highest during wet harvest seasons. Time of nitrogen application had no significant effect on yield, kernel recovery, the percentage of first-grade kernels or impurities. For sustained high yield and quality, 355 g nitrogen, or 0.8 kg urea/tree.year, applied in April—June is indicated. Agronomic and economic advantages of reducing rates of nitrogen applied to macadamia orchards are enhanced by increasingly important environmental considerations. Multiple regression analyses indicated that the rate, strategy and timing of nitrogen application, rainfall, temperature, flushing and litterfall were correlated with kernel recovery and first-grade kernels but more work is needed to elucidate the significance of these factors.

671 Impact of Southeastern Hurricanes on Peach and Pecan Orchards

Southeastern peach and pecan orchards weathered hurricanes in the 1980s and 1990s that left long-term effects on tree health and productivity. Pecan trees were affected the most, due to being blown down from strong winds and wet soils or suffering considerable damage to branches and immature nuts resulting in massive nut drops. Premature nut drop triggered or enhanced alternate bearing problems. Cultivar differences were evident in the ability of trees to withstand wind damage, with open-canopy trees being most resistant, but essentially all trees were damaged when they exceeded ≈17m in height. Hurricanes in older, alternate-bearing orchards sometimes broke enough limbs to induce sufficient vegetative regrowth to reestablish an equilibrium between sink (nuts) and source (foliage), thus enhancing yields in subsequent years. Peach trees which were less than 4.5 m tall and already harvested usually did not blow over unless the soil was very wet. However, peach trees were often twisted about the tree axis from the change in wind directions as the hurricane passed over. Afterwards, many trees leaned more than 30 °, especially trees less than 6 to 7 years of age. Root damage was significant and increased when trees were manually repositioned as additional root breakage occured from which these trees often later died. Trees not repositioned but instead retrained to vertical by pruning lived longer. Ambrosia beetles also attacked wind-stressed trees and caused a long-term decline. Slow moving hurricanes significantly damaged peach trees by waterlogging the soil, which killed roots and helped primary pathogens such as Phytophthora sp. to attack the tree crown. This was followed by secondary pathogens like Oxyporous sp., which attacked the internal woody cylinder. Initial trunk damage appeared localized; however, trees continued to die over a number of years. Experience showed that whole orchard removal on severe waterlogged sites was the best economical response.

Leaf nitrogen as a guide for fertilising macadamia

Summary. Despite the lack of evidence for a critical level of leaf nitrogen in macadamia, fertiliser management has been largely based on tentative standards for high yielding trees. Trees on a lower plane of nitrogen nutrition, however, produced higher yields of good quality nuts. This study was therefore carried out to establish the relationship between yield and nitrogen status of trees. Three rates of nitrogen fertiliser (0.5, 1.5 and 2.5 kg urea/tree . year; 230, 690 and 1150 g nitrogen respectively) were applied to macadamia trees in 1 of 5 application strategies: 1 application in April (floral initiation); 2 applications, one in April and one in June (inflorescence development); 3 applications, April, June and November (rapid nut growth and premature nut drop); 4 applications, April, June, November and January (oil accumulation); and 12 monthly split applications. Multiple applications were all equal in size. The association between high yields and low nitrogen status was confirmed. In some, but not all, years, yield was negatively correlated with leaf nitrogen, accounting for 47 and 59% of the variation in yield of commercially acceptable nuts (>19 mm diameter) in 1991 and 1993, respectively. It is therefore recommended that the standard for leaf nitrogen in macadamia be lowered from 1.4–1.5 to 1.3% under Australian conditions. These results raise concerns at the current trend for leaf nitrogen to be as high as 1.8%. It would be prudent to cease nitrogen applications on at least a small experimental block until leaf nitrogen declined to 1.3% and then maintain this level for at least 3 years and monitor yields.

Feeding by Cryptophlebia illepida and C. ombrodelta (Lepidoptera: Tortricidae) on Macadamia Nut Abortion

In paired-cage studies, husk feeding by Cryptophlebia illepida (Butler) resulted in an average twofold increase in nut drop 66 d after introduction compared with nuts that were not fed upon. This data suggested that nut immaturity could be related to Cryptophlebia spp. feeding. Field tests demonstrated that the proportion of nuts with husk damage was related to the proportion of nuts which were immature in a sample. My data show that the effect of Cryptophlebia feeding on macadamia is underestimated when only direct damage to the kernel is assessed.

432 PB 177 ADDITIONAL SYMPTOMS OF BORON DEFICIENCY IDENTIFIED IN ALMOND

Boron(B) deficiency in almond (Prunus dulcis Mill.) is characterized by leaf tip scorch, leaf drop, twig dieback, brown gummy areas in the endocarp, and embryo abortion followed by nut drop in May. Additional symptoms revealed by our work include failure of flowers to set nuts and lateral bud drop. Lack of production in part or in all of the free canopy causes spurs to elongate leading to a “willow twig” symptom on the small fruitwood. This can be confused with the nonproductive “bull” syndrome or with virus bud failure (ABFV or PRSV). Comparative leaf, pericarp, or kernel analysis in May gave a better indication of low B than did leaf analysis in August. In August, analyzing the hulls (mesocarp and exocarp) gave better separation between deficient and adequate trees than did leaf, kernel, or shell analysis. B critical levels for almond leaves should be re-evaluated since deficiency symptoms occur at currently accepted “adequate” levels.

Southern Green Stink Bug (Hemiptera: Pentatomidae) Feeding on Hawaiian Macadamia Nuts: The Relative Importance of Damage Occurring in the Canopy and on the Ground

Southern green stink bug, Nezara viridula (L.), feeding resulted in a significant increase in nut abortion rates in smaller nuts (10-28 mm diameter) but not in full-size nuts. Studies also showed that, for full-size nuts, damage can occur both in the tree canopy and on the ground, generally within 1 wk of nut drop. The magnitude of damage appears to be higher on the ground than in the canopy, suggesting that pest management programs that reduce population levels on the ground need to be implemented to decrease damage levels.

USE OF NAA AS A PECAN NUT THINNER

NAA was applied to pecan nuts at concentrations of 0, 20, 50, 100, 200, and 500 μg·g-1 on May 19, June 16, and July 20. The 500 μg·g-1 concentration induced nut drop at all dates but was phytotoxic to leaves when applied on May 19. Concentrations of 50-100 μg·g reduced preharvest drop of nuts.

Somatic embryogenesis and callus production from cotyledon explants of Eastern black walnut

Starting at 8 weeks and continuing until 23 weeks (nut drop) after anthesis,1 m2 explants from cotyledons of immature seeds were extracted from Juglans nigra fruits. Explants were placed on Woody Plant Medium with 1 g l-1 casein hydrolysate and 30 g l-1 sucrose. The explants remained in light for 4 weeks on primary media containing a 3×3 factorial of 0.05, 0.5, or 5.0 μM thidiazuron (TDZ) and 0.1, 1.0, or 10.0 μM 2,4-d. Explants were transferred to a secondary medium containing no plant growth regulators and incubated in darkness for 11 weeks. The greatest number of somatic embryos was produced 8, 10, and 12 weeks after anthesis from explants on media with 0.5 or 5.0 μM TDZ and 0.1 or 1.0 μM 2,4-d. Explants produced the greatest callus volume and dry weight 10, 12, and 14 weeks after anthesis. Throughout the study, callus generally increased with increasing concentrations of both TDZ and 2,4-d.

Timing of nitrogen application to macadamias. 1. Tree nitrogen status and vegetative growth

Nitrogen (690 g/tree.annum) was applied to 12-year-old macadamia (Macadamia integrifoloia Maiden and Betche) trees in subtropical Queensland (lat. 26�S.) at either pre-floral initiation, inflorescence development, premature nut drop or at the oil accumulation stage. Control trees received a total of 230 g of nitrogen (N) split into equal monthly applications. Leaf N concentrations in May (vegetative and reproductive dormancy) was lower in control trees (approx. 1.2%), which were visually N-deficient during winter and spring. Leaf N concentrations of all other treatments were approx. 1.3-1.4% N and leaves remained a healthy green colour throughout the year. Low N status in control trees suppressed vegetative growth (indicated by changes in trunk girth, tree height and canopy volume), effectively manipulating the vegetative:reproductive balance in favour-of the latter. The desirability of small, but frequent applications of N fertiliser to macadamias is indicated, although the optimum rate is likely to be greater than that applied to control trees in this study. It is suggested that determining tree N requirements using standard leaf nutrient levels should not be done in isolation. Tree health and vegetative growth in relation to yield, and time of sampling, particularly in relation to time of application of N and flushing peaks, should also be considered.

Effects of temperature, tree water status and relative humidity on premature nut drop from macadamia

In macadamia ( Macadamia integrifolia, Maiden and Betche), premature nut drop increased at high temperature (30 compared with 15 and 25°C). Low relative humidity (RH 40 vs. 80%) had only a slight effect at 30°C. In contrast, leaf water stress ( ψ L of −1.5 to −3.0 MPa vs. −0.5 MPa) induced more nut drop at lower temperature and high RH. Only slight cultivar differences were noted. More nuts were retained under conditions of atmospheric stress where water was non-limiting. It may therefore be possible to alleviate the effects of these stresses by strategic irrigation or overhead misting.

Inducing Macadamia Nut Drop with Ethephon

Abstract Sprays of (2-chloroethyl)phosphonic acid (ethephon), applied at the beginning of the harvest season (usually January), resulted in more than 90% nut drop of ‘Beaumont’ macadamia nuts, without causing damage to foliage or next year’s crop.